i've heard it described as the size of a safeway. >> reporter: next friday, this safeway size asteroid named da-14 is expected to pass close enough to the earth's surface to grab the attention of astronomers like ben burriss. >> they know with certainty it will come really close. it will pass within 17,200 miles of earth's surface but then cruise safely back into space. >> reporter: nasa says it is the largest to fly this close to earth since the agency started keeping track. while the experts say it won't hit the earth, 130,000 metric tons of flying mass still makes people a little nervous. >> an impact by an object the size that will pass next week happens about every 1,200 years. >> reporter: to understand the true impact of asteroids striking earth, you have to travel back 66 million years. that's the time frame researchers at uc berkeley have newly pinpointed as the demise of the dinosaurs. >> the dinosaurs we think are wiped out around 66.043 million years ago. that's to within about 320,000 years. >> reporter: in a paper published this week, the group noted along with volcanos,